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Subject[patch 18/76] x86: Clear DF before calling signal handler
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Aurelien Jarno <aurelien@aurel32.net>

x86: Clear DF before calling signal handler

The Linux kernel currently does not clear the direction flag before
calling a signal handler, whereas the x86/x86-64 ABI requires that.
This become a real problem with gcc version 4.3, which assumes that
the direction flag is correctly cleared at the entry of a function.

This patches changes the setup_frame() functions to clear the
direction before entering the signal handler.

This is a backport of patch e40cd10ccff3d9fbffd57b93780bee4b7b9bff51
("x86: clear DF before calling signal handler") that has been applied
in 2.6.25-rc.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
arch/x86/ia32/ia32_signal.c | 4 ++--
arch/x86/kernel/signal_32.c | 4 ++--
arch/x86/kernel/signal_64.c | 2 +-
3 files changed, 5 insertions(+), 5 deletions(-)

--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -494,7 +494,7 @@ int ia32_setup_frame(int sig, struct k_s
regs->ss = __USER32_DS;

set_fs(USER_DS);
- regs->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);

@@ -600,7 +600,7 @@ int ia32_setup_rt_frame(int sig, struct
regs->ss = __USER32_DS;

set_fs(USER_DS);
- regs->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);

--- a/arch/x86/kernel/signal_32.c
+++ b/arch/x86/kernel/signal_32.c
@@ -396,7 +396,7 @@ static int setup_frame(int sig, struct k
* The tracer may want to single-step inside the
* handler too.
*/
- regs->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);

@@ -489,7 +489,7 @@ static int setup_rt_frame(int sig, struc
* The tracer may want to single-step inside the
* handler too.
*/
- regs->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);

--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -295,7 +295,7 @@ static int setup_rt_frame(int sig, struc
see include/asm-x86_64/uaccess.h for details. */
set_fs(USER_DS);

- regs->eflags &= ~TF_MASK;
+ regs->eflags &= ~(TF_MASK | X86_EFLAGS_DF);
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);
#ifdef DEBUG_SIG
--


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